Conventional backpack frames attempt to provide proper balance of the load by keeping the pack load as close to the body as possible, while attempting to provide air circulation between the bearer's back and the pack load. Such frames are constructed such that heavier loads may be placed high in the pack near the shoulders, helping to balance the pack load. It is also a goal of conventional backpack frames to provide easy access to the load.
The need to provide proper balance of the pack load is of constant concern to the backpack user, because maximum load-carrying capability and maximum range are largely affected by the degree of balance obtained. One known method to help achieve balance is to place the heaviest part of the load high in the pack above the shoulders. The frame bearer then leans forward slightly to try to bring the weight over the bearer's hips so that the center of gravity of the pack load is aligned with an imaginary vertical plane passing through the hips of the bearer, hereinafter referred to as the hip line. Unfortunately, prior art frames require the user to lean forward to carry the load in a bent position in order to dispose the pack load over the hips of the bearer. The incomplete balance afforded by conventional frames increases the bearer's work in carrying the load, and the exertion necessary to meet such increased work demands limit the bearer's maximum load-carrying capability and range below that which could be gained with perfect balance and upright posture.
Various mechanisms have been developed in the prior art in an attempt to improve the situation, as shown, for example, in the patent to Fenner, U.S. Pat. No. 4,087,031. Typical backpack frames are described in publications directed to camping and backpacking. For example, Backpacker. February 1991, pp. 59-64, includes a review and rating of commercially available backpacks. A somewhat similar collection of commercially available backpacks is provided in Camping Mail Order Catalog, 1990, pp. 9-13.
Known backpack improvements suffer from one or both of two serious shortcomings:
1) they do not allow positioning or counterbalancing of the center of gravity of the pack load over the bearer's hip line in the postures that the bearer must choose for the various terrains and conditions that the bearer encounters; and
2) in shifting the pack load by bending to bring the upper part of the load forward as a partial counterbalance, the lower part of the load is often moved further back from the body. Both of these disadvantages are substantially eliminated or at least minimized by the present invention.
Backpack frames are also known to provide water storage as a means of providing drinking water in remote areas. Such packs generally require the bearer to remove the backpack frame or the assistance of another to gain access to the water. The present invention provides a construction which allows the bearer to quench his thirst on the move without disrupting his effort.